/*
Merge two sorted linked lists and return it as a new list. The new list should be made by splicing together the nodes of the first two lists.
 */

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode(int x) : val(x), next(NULL) {}
 * };
 */
class Solution {
public:
    ListNode *mergeTwoLists(ListNode *l1, ListNode *l2) {
        //if (!l1) return l2; if (!l2) return l1;
        ListNode head(-1), *ptr = &head;
        while (l1 && l2) {
            if (l1->val <= l2->val) {ptr->next = l1; l1=l1->next;}
            else {ptr->next = l2; l2=l2->next; }
            ptr = ptr->next;
        }
        if (l1) ptr->next = l1;
        if (l2) ptr->next = l2;
        return head.next;
    }
};
